Part of the goal of Bridle’s project was to interrogate the notion of the “smart home” or “smart city” that’s regularly portrayed as a social and technological ideal. But as Bridle notes in an essay he wrote about his experience, new technological advances also encourage new ways to police people.

Bridle set out to track “Automated Number Plate Recognition” cameras–which help London operate its congestion pricing plan–along the site of the first London Wall, an ancient barrier built by the Romans to protect the inner city. But after a few miles of tracking the remnants of the old wall and taking photos of cameras last month, two hotel security guards stopped Bridle and placed him under citizen’s arrest.

Police warned Bridle that casing Central London with a camera might qualify as “going equipped,” a quaintly British category of criminality meant to punish people who plan burglaries. After some explaining, the police let Bridle off. His partially completed heat map, called Paranoid Cartography, now lives here.

“I haven’t completed the project, but I already photographed 427 odd cameras. I expect that number to double [when I finish],” Bridle says. “The main symptom of paranoia is that you’re being watched all the time, but you are watched all the time. So what do we do in the situation where that’s the case?”

Bridle’s bread and butter is turning today’s justified paranoia into art. But his work also hints at a frightening vision of the future. In contrast to the old wall, a single structure meant to keep London secure, Bridle imagines that future surveillance and security technologies will likely become even more integrated into the landscape–and more invisible.

By way of example, Bridle forecasts what a “Sixth Wall” might look like, a futuristic riff on the Romans’ old idea. In Bridle’s vision, the Sixth Wall functions more like a surveillance fabric, something inextricable from our bodies, even. He writes:

The Sixth Wall will be made of intelligent dust which settles in the folds of your clothes and communicates your position and heart rate to orbiting satellites. London’s citizens will dream, and the images of their dreams will dance on the telescreens of Piccadilly Circus, and be found wanting.